69,714 research outputs found
New Cosmological Structures on Medium Angular Scales Detected with the Tenerife Experiments
We present observations at 10 and 15 GHz taken with the Tenerife experiments
in a band of the sky at Dec.=+35 degrees. These experiments are sensitive to
multipoles in the range l=10-30. The sensitivity per beam is 56 and 20 microK
for the 10 and the 15 GHz data, respectively. After subtraction of the
prediction of known radio-sources, the analysis of the data at 15 GHz at high
Galactic latitude shows the presence of a signal with amplitude Delta Trms ~ 32
microK. In the case of a Harrison-Zeldovich spectrum for the primordial
fluctuations, a likelihood analysis shows that this signal corresponds to a
quadrupole amplitude Q_rms-ps=20.1+7.1-5.4 microK, in agreement with our
previous results at Dec.+=40 degrees and with the results of the COBE DMR.
There is clear evidence for the presence of individual features in the RA range
190 degrees to 250 degrees with a peak to peak amplitude of ~110 microK. A
preliminary comparison between our results and COBE DMR predictions for the
Tenerife experiments clearly indicates the presence of individual features
common to both. The constancy in amplitude over such a large range in frequency
(10-90 GHz) is strongly indicative of an intrinsic cosmological origin for
these structures.Comment: ApJ Letters accepted, 13 pages Latex (uses AASTEX) and 4 encapsulated
postscript figures
The Tenerife Cosmic Microwave Background Maps: Observations and First Analysis
The results of the Tenerife Cosmic Microwave Background (CMB) experiments are
presented. These observations cover 5000 and 6500 square degrees on the sky at
10 and 15 GHz respectively centred around Dec.~ +35 degrees. The experiments
are sensitive to multipoles l=10-30 which corresponds to the Sachs-Wolfe
plateau of the CMB power spectra. The sensitivity of the results are ~31 and
\~12 microK at 10 and 15 GHz respectively in a beam-size region (5 degrees
FWHM). The data at 15 GHz show clear detection of structure at high Galactic
latitude; the results at 10 GHz are compatible with these, but at lower
significance. A likelihood analysis of the 10 and 15 GHz data at high Galactic
latitude, assuming a flat CMB band power spectra gives a signal Delta
T_l=30+10-8 microK (68 % C.L.). Including the possible contaminating effect due
to the diffuse Galactic component, the CMB signal is Delta T_l=30+15-11 microK.
These values are highly stable against the Galactic cut chosen. Assuming a
Harrison-Zeldovich spectrum for the primordial fluctuations, the above values
imply an expected quadrupole Q_RMS-PS=20+10-7 microK which confirms previous
results from these experiments, and which are compatible with the COBE DMR.Comment: 17 pages, 7 figures. Submitted to Ap
Sources of sport confidence, imagery type and performance among competitive athletes: The mediating role of sports confidence
Aim: This study explored the mediating role of sport confidence upon (1) sources of sport confidence-performance relationship and (2) imagery-performance relationship. Methods: Participants were 157 competitive athletes who completed state measures of confidence level/sources, imagery type and performance within one hour after competition. Results: Among the current sample, confirmatory factor analysis revealed appropriate support for the nine-factor SSCQ and the five-factor SIQ. Mediational analysis revealed that sport confidence had a mediating influence upon the achievement source of confidence-performance relationship. In addition, both cognitive and motivational imagery types were found to be important sources of confidence, as sport confidence mediated imagery type-performance relationship. Conclusion: Findings indicated that athletes who construed confidence from their own achievements and report multiple images on a more frequent basis are likely to benefit from enhanced levels of state sport confidence and subsequent performance
Sources of sport confidence, imagery type and performance among competitive athletes: The mediating role of sports confidence
Aim: This study explored the mediating role of sport confidence upon (1) sources of sport confidence-performance relationship and (2) imagery-performance relationship. Methods: Participants were 157 competitive athletes who completed state measures of confidence level/sources, imagery type and performance within one hour after competition. Results: Among the current sample, confirmatory factor analysis revealed appropriate support for the nine-factor SSCQ and the five-factor SIQ. Mediational analysis revealed that sport confidence had a mediating influence upon the achievement source of confidence-performance relationship. In addition, both cognitive and motivational imagery types were found to be important sources of confidence, as sport confidence mediated imagery type-performance relationship. Conclusion: Findings indicated that athletes who construed confidence from their own achievements and report multiple images on a more frequent basis are likely to benefit from enhanced levels of state sport confidence and subsequent performance
Transport of infrared radiation in cuboidal clouds
The transport of infrared radiation in a single cuboidal cloud using a vertical two steam approximation was modeled. The emittance of the top face of the model cloud is always less than that for a plane parallel cloud of the same optical depth. The hemisphere flux escaping from the cloud top has a gradient from the center to the edges which brighten when the cloud is over warmer ground. Cooling rate calculations in the 8 to 13.6 micrometer region show that there is cooling from the sides of the cloud at all levels even when there is heating of the core from the ground below. The radiances exiting from model cuboidal clouds were computed by path integration over the source function obtained with the two stream approximation. It is suggested that the brightness temperature measured from finite clouds will overestimate the cloud top temperature
How effective is harassment on infalling late-type dwarfs?
A new harassment model is presented that models the complex, and dynamical
tidal field of a Virgo like galaxy cluster. The model is applied to small,
late-type dwarf disc galaxies (of substantially lower mass than in previous
harassment simulations) as they infall into the cluster from the outskirts.
These dwarf galaxies are only mildly affected by high speed tidal encounters
with little or no observable consequences; typical stellar losses are ,
producing very low surface brightness streams ( mag arcsec),
and a factor of two drop in dynamical mass-to-light ratio. Final stellar discs
remain disc-like, and dominated by rotation although often with tidally induced
spiral structure. By means of Monte-Carlo simulations, the statistically likely
influences of harassment on infalling dwarf galaxies are determined. The
effects of harassment are found to be highly dependent on the orbit of the
galaxy within the cluster, such that newly accreted dwarf galaxies typically
suffer only mild harassment. Strong tidal encounters, that can morphologically
transform discs into spheroidals, are rare occurring in of dwarf
galaxy infalls for typical orbits of sub-structure within CDM cluster
mass halos. For orbits with small apocentric distances (250 kpc), harassment
is significantly stronger resulting in complete disruption or heavy mass loss
( dark matter and stellar), however, such orbits are expected
to be highly improbable for newly infalling galaxies due to the deep potential
well of the cluster.Comment: 15 pages, 11 figures, 4 table
RTS amplitudes in decananometer MOSFETs: 3-D simulation study
In this paper we study the amplitudes of random telegraph signals (RTS) associated with the trapping of a single electron in defect states at the Si/SiO/sub 2/ interface of sub-100-nm (decananometer) MOSFETs employing three-dimensional (3-D) "atomistic" simulations. Both continuous doping charge and random discrete dopants in the active region of the MOSFETs are considered in the simulations. The dependence of the RTS amplitudes on the position of the trapped charge in the channel and on device design parameters such as dimensions, oxide thickness and channel doping concentration is studied in detail. The 3-D simulations offer a natural explanation for the large variation in the RTS amplitudes measured experimentally in otherwise identical MOSFETs. The random discrete dopant simulations result in RTS amplitudes several times higher compared to continuous charge simulations. They also produce closer to the experimentally observed distributions of the RTS amplitudes. The results highlight the significant impact of single charge trapping in the next generation decananometer MOSFETs
Hierarchical approach to 'atomistic' 3-D MOSFET simulation
We present a hierarchical approach to the 'atomistic' simulation of aggressively scaled sub-0.1-μm MOSFETs. These devices are so small that their characteristics depend on the precise location of dopant atoms within them, not just on their average density. A full-scale three-dimensional drift-diffusion atomistic simulation approach is first described and used to verify more economical, but restricted, options. To reduce processor time and memory requirements at high drain voltage, we have developed a self-consistent option based on a solution of the current continuity equation restricted to a thin slab of the channel. This is coupled to the solution of the Poisson equation in the whole simulation domain in the Gummel iteration cycles. The accuracy of this approach is investigated in comparison to the full self-consistent solution. At low drain voltage, a single solution of the nonlinear Poisson equation is sufficient to extract the current with satisfactory accuracy. In this case, the current is calculated by solving the current continuity equation in a drift approximation only, also in a thin slab containing the MOSFET channel. The regions of applicability for the different components of this hierarchical approach are illustrated in example simulations covering the random dopant-induced threshold voltage fluctuations, threshold voltage lowering, threshold voltage asymmetry, and drain current fluctuations
- …